Chapter Two
Exploring the UNIX/Linux
File Systems and File
Security
Guide To UNIX Using Linux
Fourth Edition
Chapter 2 Unix (31 slides)
CTEC 110
1
Objectives
•
•
•
•
•
•
•
•
•
Discuss UNIX/Linux file systems
Explain partitions and inodes
Understand the elements of the root hierarchy
Use the mount command
Explain and use paths, pathnames, and prompts
Navigate the file system
Create and remove directories
Copy and delete files
Configure file permissions
Chapter 2 Unix (31 slides)
CTEC 110
2
Understanding UNIX/Linux
File Systems
•
•
•
File: basic component for data storage
– UNIX/Linux considers everything to be a file
A file system is UNIX/Linux’s way of organizing
files on mass storage devices
– A physical file system is a section of the hard
disk that has been formatted to hold files
The file system is organized in a hierarchical
structure (inverted tree)
Chapter 2 Unix (31 slides)
CTEC 110
3
Understanding UNIX/Linux
File Systems (continued)
Chapter 2 Unix (31 slides)
CTEC 110
4
Understanding the Standard Tree
Structure
•
•
•
The structure starts at the root level
– Root is the name of the file at this basic level
and it is denoted by the slash character (/)
Directory: file that can contain other files and
directories
Subdirectory: directory within a directory
– The subdirectory is considered the child of the
parent directory
Chapter 2 Unix (31 slides)
CTEC 110
5
Using UNIX/Linux Partitions
•
•
The section of the disk that holds a file system is
called a partition
– When installing UNIX/Linux, one of the first
tasks is deciding how to partition a storage
device, or hard disk
– Hard disks may have many partitions
UNIX/Linux partitions are given names
– LINUX uses hda1 and hda2
Chapter 2 Unix (31 slides)
CTEC 110
6
Using UNIX/Linux Partitions (continued)
•
•
Storage devices are called peripheral devices
Peripheral devices connect to the computer
through electronic interfaces
– IDE: Integrated Drive Electronics
– SCSI: Small Computer System Interface
Chapter 2 Unix (31 slides)
CTEC 110
7
Chapter 2 Unix (31 slides)
CTEC 110
8
Setting Up Hard Disk Partitions
•
•
•
Partitioning your hard disk provides organized space
for file systems
At least 3 partitions (root, swap, /boot) often
recommended
Root partition holds root file system directory (/), size
depends on installation but often ranges between 1.2
to 5+ GB
Chapter 2 Unix (31 slides)
CTEC 110
9
Setting Up Hard Disk Partitions
(continued)
•
•
•
Swap partition acts as a memory extension, often has
same size as RAM, enables virtual memory
/boot partition used to store the os files comprising
the kernel and is relatively small
Other used partitions include /usr, /home, /var
Chapter 2 Unix (31 slides)
CTEC 110
10
Using Inodes
•
•
•
Inodes are associated with directories and files in ufs
and ext file systems
An inode contains the name, general information,
and location information (a pointer) for a file or
directory
A superblock contains information about the block
layout on a specific partition
Chapter 2 Unix (31 slides)
CTEC 110
11
Exploring the Root Hierarchy
•
•
•
UNIX/Linux must mount a file system before any
programs can access files on it
To mount a file system is to connect it to the
directory tree structure
The root file system is mounted by the kernel
when the system starts
Chapter 2 Unix (31 slides)
CTEC 110
12
Exploring the Root Hierarchy
(continued)
•
The root directory contains sub-directories that contain
files:
– /bin contains binaries, or executables needed to
start the system and perform system tasks
– /boot contains files needed by the bootstrap
loader as well as kernel images
– /dev contains system device reference files
Chapter 2 Unix (31 slides)
CTEC 110
13
Chapter 2 Unix (31 slides)
CTEC 110
14
Exploring the Root Hierarchy
(continued)
•
Root subdirectories continued:
– /etc contains configuration files that the system
uses when the computer starts
– /lib contains kernel modules, security
information, and the shared library images
– /mnt contains mount points for temporary
mounts by the system administrator
– /proc is a virtual file system allocated in memory
only
Chapter 2 Unix (31 slides)
CTEC 110
15
Exploring the Root Hierarchy
(continued)
•
Root subdirectories continued:
– /root is the home directory of the root user, or
the system administrator
– /sbin contains essential network programs used
only by the system administrator
– /tmp is a temporary place to store data during
processing cycles
– /var contains subdirectories which have sizes
that often change, such as error logs
Chapter 2 Unix (31 slides)
CTEC 110
16
Using the mount Command
•
•
•
Users can access mounted file systems which they
have permission to access
Additional file systems can be mounted at any
time using the mount command
To ensure system security, only the root user uses
the mount command
Chapter 2 Unix (31 slides)
CTEC 110
17
Using Paths, Pathnames, and Prompts
•
To specify a file or directory, use its pathname,
which follows the branches of the file system to
the desired file
– A forward slash (/) separates each directory
name
– The UNIX/Linux command prompt may indicate
your location within the file system
– Use the UNIX/Linux pwd command to display
the current path name
Chapter 2 Unix (31 slides)
CTEC 110
18
Chapter 2 Unix (31 slides)
CTEC 110
19
Chapter 2 Unix (31 slides)
CTEC 110
20
Navigating the File System
•
•
To navigate the UNIX/Linux directory structure,
use the cd (change directory) command
UNIX/Linux refers to a path as either:
– Absolute - begins at the root level and lists all
subdirectories to the destination file
– Relative - begins at your current working
directory and proceeds from there
Chapter 2 Unix (31 slides)
CTEC 110
21
Using Dot and Dot Dot Addressing
Techniques
•
•
•
UNIX/Linux interpret a single dot (.) to mean the
current working directory
Two dots (..) mean the parent directory
cd .. moves you up a level in the directory structure
Chapter 2 Unix (31 slides)
CTEC 110
22
Listing Directory Contents
The ls (list)
command
displays a
directory’s
contents,
including files
and
subdirectories
Chapter 2 Unix (31 slides)
CTEC 110
23
Using Wildcards
•
•
•
A wildcard is a special character that is used as a
placeholder
The * wildcard represents any group of characters in
a file name
The ? wildcard represents a single character in a file
name
Chapter 2 Unix (31 slides)
CTEC 110
24
Creating and Removing
Directories and Files
•
•
•
•
mkdir (make directory) command
– Create a new directory
rmdir (remove directory) command
– Delete an empty directory
cp (copy) command
– Copy files from one directory to another
rm (remove) command
– Delete files
Chapter 2 Unix (31 slides)
CTEC 110
25
Configuring File Permissions
for Security
Chapter 2 Unix (31 slides)
CTEC 110
26
Configuring File Permissions
for Security (continued)
File Permissions
Chapter 2 Unix (31 slides)
CTEC 110
r
Owner has read
w
Owner has write
x
Owner has execute
r
Group has read
-
Group does not have write
x
Group has execute
r
Others have read
-
Others do not have write
x
Others have execute
27
Configuring File Permissions
for Security (continued)
•
•
chmod command
– To set file permissions
– Settings are read (r), write (w), execute (x)
– The three types of users are owners(users),
groups, and others(world) or simply (ugo)
Setting permissions to directories
– Use the execute (x) to grant access
Chapter 2 Unix (31 slides)
CTEC 110
28
Chapter 2 Unix Exercises
•
Work through Hands-on Projects at
end of chapter 2
•
Canvas: Review Questions 2
– (Do not do questions 22,23,24 and 25)
•
Read chapter 3 before next class session
• Quiz 2 Unix…
Chapter 2 Unix (31 slides)
CTEC 110
31